MTR and Dravet syndrome: Polymorphisms of genes encoding cobalamin-transporting proteins such as transcobalamin 2 (TC2) may interfere with the availability of this vitamin in the organism.16,17 Cobalamin (vitamin B12) plays an important role in folate metabolism because of its action as cofactor for methionine synthase (MTR) enzyme.18 Thus, genetic variants in the TC2 gene possibly have an influence on cellular methylation reactions and on the risk that the mother may bear a DS child.